Air diffuser

ABSTRACT

A linear air diffuser is disclosed for the delivery of conditioned air to the interior of a passenger vehicle such as a bus, railcar or the like. The diffuser consists of a frame structure characterized by a pair of open ended longitudinally extending delivery channels situated in a generally parallel side-by-side relationship. Each of the channels is turned to extend laterally outwardly in opposite directions and is provided with a curved interior surface on one wall to intercept input air so as to induce eddy current turbulence in the flow characteristics of the delivered air. The input openings to the channels are partially closed by a common longitudinal plate releasably affixed to the frame structure. The lateral peripheral edges of the plate serve to determine the width of a narrow longitudinal input orifice for each of the channels.

This is a continuation of application Ser. No. 934,907, filed Aug. 18,1978, now abandoned.

BACKGROUND OF THE INVENTION

Air-conditioning systems for public transportation vehicles pose specialdesign problems and challanges. Such a system must be capable ofoffsetting to an established degree the relatively high heat loadexpected to be generated by the maximum density of passengers for whichthe vehicle is designed. Conditioned air must therefore be delivered tothe passenger cabin at a relatively high cooling rate. For example, withrespect to a railcar of approximately 5400 cubic feet, typical coolingspecifications require conditioned air to be delivered at the rate ofabout 3600 cubic feet per minute (C.F.M.) which is equal to a completeair change within the vehicle every 1.5 minutes (approximately fivetimes the rate of a normal residential cooling system).

At such delivery rates, significant problems occur with respectpassenger comfort. Precise control over the direction of air flow withinthe vehicle cabin, and in particular with respect to the air flow in thevicinity of the diffuser outlet must be exercised. Since circulatingvelocities within the vehicle must be relatively high, impingement ofthe circulating air upon the passengers (particularly those located inproximity to the diffuser outlet) must be avoided in order to preservetheir comfort.

Heretofore, vehicle air-conditioning systems have employed a pluralityof interconnected air-diffusing outlets distributed throughout thevehicle passenger cabin at predetermined locations. Unfortunately, suchprior arrangements have been found to result in undesirable drafts onpassengers situated in the vicinity of the outlets, particularly withrespect to standing passengers.

One technique which has been utilized heretofore for lowering thevelocities at which conditioned air exits from the diffusing outlet(without affecting the cooling rate) is to provide a linear diffuserelement which extends continuously along the full length of the vehiclefrom one end to the other. It is well understood that such a diffuserdelivers air at exit velocities which (for a given cooling rate) areless than those which would be present at each of a group of disburseddiffuser outlets as described above.

However, even the use of linear air diffusers has generally failedheretofore to satisfy several basic requirements for adequate passengercomfort. These requirements are essentially as follows:

(1) the rate at which the linear diffuser delivers conditioned air tothe vehicle cabin must be substantially uniform throughout the length ofthe diffuser;

(2) the direction in which conditioned air exits from the diffuseroutlets must be carefully controlled to avoid its being dumped onto thepassengers; and

(3) conditioned air delivered by the air-conditioning system must beadapated to mix thoroughly with ambient air of a different temperaturewithin the vehicle.

An air conditioning system for public vehicles which satisfies all ofthese basic requirements has not been available heretofore. While it hasbeen possible to achieve generally uniform delivery rates, none of theprior systems has been able to avoid to any significant extent,impingement of the conditioned air directly upon the passengers,particularly the standing passengers and those located proximate to theair delivery outlets.

These and other disadvantages of the prior types of air diffusers areobviated by the present invention in which the diffuser or air deliverynozzle is adapted to effect selected turbulence characteristics in thedelivered air such that it tends principally to flow laterally outwardlyalong the celing plane of the vehicle toward the side walls of thecabin. The delivered air is thereafter turned downward by the cabinwalls and circulates generally along the cabin periphery. The ambientair within the cabin is drawn into the circulatingtemperature-controlled air and is mixed therewith to effectcomprehensive cooling of the cabin. The stream of conditioned aircreates a shear effect as it passes over the inner surfaces of thevehicle ceiling and walls thereby to generate an additional degree ofturbulence which facilitates the mixing.

In accordance with the invention, the output nozzle of the presentdiffuser is adapted to generate a cyclical or whirling turbulence withinthe delivered air flow. Such eddy current tubulence not only assists inmixing the ambient and delivered air, but causes the delivered air tohang near the ceiling as it moves outwardly toward the cabin wallsrather than to drop onto nearby passengers. As a result, efficientcooling of the cabin is achieved without generating uncomfortable draftson the passengers.

These and other objectives of the present invention are obtained byproviding a linear air diffuser which extends longitudinally along thelength of the passenger vehicle at its ceiling. In one embodiment of theinvention, the diffuser nozzle includes a pair of outwardly diverginglongitudinal output channels defined in part by the sidewalls of acentral rail or vane of generally Y-shaped cross-sectionalconfiguration. The sidewalls are shaped into a pair of back-to-backgenerally concave external surfaces each of which forms one inerior wallof each of the output channels. A pair of substantially U-shapedlongitudinal side rail members coextensive with the central rail areconnected to opposite sides thereof in spaced relation to the concavesurfaces and open laterally outwardly in opposite directions. Theinwardly facing continuous surface areas of the base section andlaterally extending lower flange of each of the side rails forms theother interior wall of each of the output channels. Each of the lowerflanges may be provided with generally planar section which is parallelto and overlies for a predetermined distance the opposite interior wallof the channel near the output opening. Air entering the two channels attheir inner ends is deflected to flow laterally outwardly away from thediffusor in substantially opposite directions.

Entrance of pressurized air to the two channels at their respectiveinner ends is controlled by each of a pair of generally parallel orificeslots or openings which extend longitudinally along the length of thediffuser. In one embodiment, the orifice openings are defined on oneside by the longitudinal peripheral edges of a substantially flatorifice plate centered at the top of the central rail and coextensivetherewith. The other side of each of the orifice openings is determinedby an opposing peripheral edge formed along each of the side rails.

In accordance with the invention, the size of the orifice openings maybe fixed, by adjusting the plate width in relationship to the staticpressure of conditioned air available within the system upstream of theoutput nozzle. In this way, a desired delivery rate for the diffuser(determined by the orifice opening) may be achieved for a given airsupply pressure, such that the delivery rate remains consistentthroughout the vehicle length.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the present invention, reference may behad to the accompanying drawings in which:

FIG. 1 is an exploded view of an air diffuser in accordance with theinvention;

FIG. 2 is a perspective view of the air diffuser of FIG. 1.

FIG. 3 is a top plan view of the air diffuser of FIG. 1; and

FIG. 4 is a cross-section taken along the line 4--4 of FIG. 3.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, and in particular to FIGS. 1 and 4, thereis illustrated a linear air diffuser assembly generally indicated byreference numeral 10, having an input side 11 and an output side 12. Thediffuser is designed to interface with an air supply plenum or duct 15usually situated above the ceiling of a passenger vehicle such as arailcar or bus, and generally extending along the entire length of thevehicle. A typical duct system of the average railcar for example, mayextend for a length of approximately 50 feet or more along the top ofthe vehicle. Conditioned air is supplied to the duct under pressure andenters the diffuser through its input side 11. The output side 12 facesdownwardly into the vehicle passenger cabin and, in accordance with thepresent invention, is adapted to distribute the conditioned air in aparticular flow pattern, described below, along the length of the cabin.

In the present embodiment, the diffuser 10 is characterized by anelongated central rail or vane 13 which is preferably formed of aluminumby an extrusion process in modular section lengths as established by thetotal length of the supply duct system servicing the passenger cabin.The rail 13 is provided with a flat longitudinal upper surface 14 whichis joined along its opposite longitudinal edges by a pair of generallydownwardly directed side walls 16 and 17. The sidewalls 16 and 17 aresubstantially straight in the vicinity of the upper surface 14, butgradually blend into laterally outwardly diverging curvilinear sections18 and 19 respectively, which flare apart for approximately equaldistances from the center of the rail. The radius of curvature for eachof the sections 18 and 19 is substantially the same, and the wallsgradually straighten out as they approach their respective lateraledges. The side walls 16 and 17 may also be turned or bent inwardlybelow their curved outer surfaces to define a pair of opposing generallystraight horizontal sections 23 and 24 which face the interior of thepassenger cabin. The sections 23 and 24 terminate in spaced apartrelation to define a central longitudinal gap or slot 26. The rail 13 ispreferably hollow to conserve weight.

In the present embodiment, the rail 13 is fitted with a plurality ofoverlying transverse spacers 29 which are centered on the upper surface14 and which extend equally in opposite directions laterally outwardlytherefrom. Each of the spacers is provided with a flat upper surface 31and a pair of depending substantially parallel mounting walls 32 and 33which overlie the innermost generally upright portions of the sidewalls16 and 17 respectively. The spacers 29 are preferably hollow to conserveweight, and in that case may be provided with interior locating ribs 30aand 30b which straddle the upper surface 14 of the rail 13 to ensurereliable positioning of the center of the spacer at the top of thecentral rail. Under these conditions, the spacers 29 may also beprovided with lower inwardly directed flanges 34 and 36 to abut againstthe sidewalls 16 and 17 for additional stability.

Each of the spacers may be secured to the rail 13 by means of a threadedbolt 37 which extends upwardly through the rail and spacer to be engagedexternally by a cooperating nut 38. Access to the head of the bolt 37for assembly purposes is provided through the longitudinal slot 26.

Identical generally U-shaped side rails 41 and 42 are affixed onopposite sides of the central rail 13 to the spacers 29. The arrangementis such that the side rails, which are coextensive with the centralrail, open laterally outwardly in opposite directions. Each of the siderails is provided with a relatively straight internal base section 43and 44, respectively, which abuts against and is secured to acorresponding one of the depending mounting walls 32 and 33 of each ofthe spacers 29. The mounting walls are preferably provided with externalnotches 45a and 45b to receive corresponding locating lugs on the basesections of the side rails. This arrangement insures accurate spacing ofeach portion of the side rail geometry with respect to the central rail13. The side rails may be secured to the spacers by a single transversebolt 50 and fastener 50a. The bolt may pass through the assemblylaterally from either direction, and a clearance notch 50b may beprovided in the central rail to receive the bolt and also allow removalof the rail 13 for servicing or adjustment of air flow, if required,without disturbing the remainder of the assembly.

Lower legs or flanges 46 and 47, respectively, of the side rails 41 and42 extend obliquely outwardly from their respective base sections indiverging directions which correspond substantially to the directionsassumed by the underlying sidewalls 16 and 17 of the central rail 13.The spacing between the sidewalls 16 and 17 of the central rail 13 andthe overlying side rails 41 and 42 remains substantially constant alongthe length of the sidewalls 16 and 17 thereby to define identical airdiffusion channels 48 and 49 therebetween on opposite sides of thecentral rail. The effective length of the channels 48 and 49 andconsequently the output flow characteristics of the diffuser areaffected by the lateral extent and direction of the flanges 46 and 47.

In the present embodiment, the flanges 46 and 47 are each characterizedby a substantially flat inwardly facing surface area 51 and 52,respectively. Each of the areas 51 and 52 substantially parallels theopposing relatively straight lower segment of respective sidewalls 16and 17 and extends outwardly thereof so as to define the output openingsfor the diffusion channels and to control the air delivery velocity andother flow characteristics of air exiting from the diffuser.

It will be understood that the invention is not to be limited to anyparticular geometry for the deflective flanges 46 and 47 and that thelength of the diffusion channels between their input and output openingsmay be empirically determined in advance to satisfy the knownspecification for each particular air conditioning system.

Upper legs 53 and 54 of the side rails 41 and 42, respectively, aregenerally utilized for mounting the diffuser assembly adjacent the airplenum 15 in the ceiling of the passenger vehicle. Accordingly, theirconfiguration may likewise be varied to take into account the mountingrequirements for any particular installation.

With reference to FIGS. 2 and 3, an elongated substantially planarorifice plate 56 is situated adjacent the top of the central rail 13 tooverlie to a predetermined extent the input end of each of the diffusionchannels 48 and 49. Alternatively, a pair of similar plates might beutilized such that one overlies each of the diffusion channels. Theorifice openings might be adjusted by sliding the plates laterally backand forth over the import openings to the channels. One plate might beskewed relative to the other to taper the orifice opening, as desired.

The plate 56 is substantially coextensive with the rail 13 and restsalong the upper surfaces 31 of each of the several spacers 29. Wheredesired, a cork layer 55 may be provided between the orifice plate andthe central rail to insure uniform support beneath the plate along thelength of the diffuser unit. The plate is releasably secured in positionby the bolts 37 and cooperating nuts 38.

The width of the orifice plate 56 is such that its lateral peripheraledges 57 and 58 are spaced a predetermined distance from adjacentperipheral edges of the corresponding side rail base sections 43 and 44.This spacing defines a pair of longitudinal input orifices 59 and 61which may be of equal or unequal areas, one for each of the diffusionchannels 48 and 49 to control the rate at which conditioned air entersthe diffusion channels for distribution into the vehicle cabin. In thepreferred embodiment, the input orifices 59 and 61 extend continuouslyalong the entire length of the diffuser element 10 in parallelrelationship, although each may also consist of a colinear series ofdiscrete longitudinal slots if necessary.

The dimensions of the input orifice are determined in advance ofinstallation of the diffuser in accordance with the knowncharacteristics of the air supply fan source (not shown) anddistribution duct or plenum geometry for the air conditioning system forwhich the diffuser is being tailored. The orifice size is chosen (byadjusting the size of the orifice plate 56) so as to enable the diffuserto deliver conditioned air consistently along its length at the desiredor specified C.F.M. delivery rate. In general, the orifice size isselected by matching as closely as possible with the specified outputrate to be achieved by the system, emperically derived output rates forseveral proposed orifice openings (with respect to a given section ofdiffuser).

In addition with respect to human comfort systems, it has been foundexperimentally that for a given orifice opening, the output deliveryrate of the diffuser in C.F.M. per foot length of diffuser varieslinearly with the static pressure of conditioned air within the supplyduct. A family of related calibration curves for particular orificeopenings may thus be generated for appropriate reference in confirmingadequate system performance. Thus, air delivery rates (C.F.M.) in anygiven longitudinal location may be accurately established by a singlemeasurement of static pressure at the subject location. This valueprovides a more precise verification of diffuser output due to itsmagnitude and stability. This technique avoids the measurement of exitair velocities, heretofore required, which are normally quite variableand indeterminate.

In general, the longitudinal orifices 59 and 61 open into the fixed airplenum or supply duct 15 situated above the diffuser element and intowhich conditioned air is forced from one end by a suitable fan or thelike (not shown). It has been found that the geometry of this supplyduct plays a significant role in the ultimate C.F.M. delivery rate ofthe diffuser element. Accordingly, it is desirable to correlate theshape of the orifice opening to the geometry of the supply duct withwhich the diffuser is tailored to interface. For example, if, as iscommon, the supply duct is tapered so as gradually to constrict itsvolume at the end opposite the air supply fan, it has been found thatthe orifice openings may remain substantially uniform along the lengthof the diffuser to insure a constant flow rate through the diffusionchannels. The tapered geometry of the supply duct insures a relativelyconstant internal air supply pressure along the length of the ductdespite the gradual air supply depletion as air passes through thediffuser into the vehicle cabin.

On the other hand, where the geometry of the air supply duct is suchthat its volume remains substantially uniform along its length, it ispreferable to taper the orifice openings such that they are narrow atthe input end of the duct and gradually enlarge by a predeterminedamount as they approach the opposite end. Thus, the tapered orificeopening compensates for the variation in air supply pressure along thelength of the uniform duct to provide a consistent delivery rate at allpoints along the diffuser.

In operation, pressurized conditioned air from the air supply ductenters the diffuser through input orifices 59 and 61. In accordance withknown physical principles, the velocity of the air increases as itpasses through the orifice constrictions and the air expands within thediffusion channels 48 and 49 to impinge upon the curvilinear inner sidewalls 16 and 17 of the central rail 13. Considering the diffusionchannel 48, for example, it will be seen that the air flow velocityadjacent the curved section of the interior channel wall is greater thanthe flow velocity at other points within the channel. This phenomenonserves to generate a vortex or eddy current turbulence within thechannel such that the air begins to circulate or whirl in acounterclockwise direction as it moves toward the outlet of the channel.Such turbulence in the air exiting from the channel causes it to tend tohug the adjacent ceiling of the vehicle as it expands laterallyoutwardly along the ceiling plane toward the vehicle walls. A similareffect is achieved as a result of corresponding turbulence generatedwithin the diffusion channel 49. Downward flow components in thedelivered air are therefore reduced so that the air remains near theceiling and avoids impingement upon passengers seated beneath orstanding near the diffusion outlet. Moreover, the swirling turbulenceeffects adequate mixing of the conditioned air and the ambient airwithin the vehicle to provide the requisite cooling rate.

Various changes and modifications will occur to those skilled in theart. For example, the present invention need not be limited to themulti-section diffuser assembly described above. One or more elements ofthe diffuser may be formed together as a single common piece or in theform of sub-assemblies, with orifice openings then being sawed, milledor routed as necessary. It is therefore intended that the scope of thepresent invention is not to be limited except as defined by thefollowing claims.

What is claimed is:
 1. A linear air diffuser for distributing a volumeof air under pressure in a uniform output flow of controlled velocityand direction comprising:a frame structure defining a pair oflongitudinal air carrying channels situated in substantially parallelside by side relationship, each of said channels having an input orificeprogressively narrowing in width along the length thereof forcontrolling the input of air to said channel substantially linearlyalong the length of the channel and having a lower portion which extendsobliquely to the plane of its input orifice such that the channelsdiverge laterally outwardly in substantially opposite directions, saidinput orifices being defined in part by the lateral peripheral edges ofa flat plate affixed to the frame and overlying a predetermined portionof a respective input side of each of said channels; a side rail,extending longitudinally parallel to and defining one side of each ofsaid channels, said rail having a downwardly directed side wall and alower flange; a defelctor vain, extending longitudinally parallel to anddefining another side of each of said channels, said vain having an airturning surface merging into a laterally outwardly directed lowersection which extends to a lateral edge thereof below the lower flangeof the side rail to define an air output nozzle that delivers the airtraversing said channel in a principally lateral direction.